Chemical processing operations, including petroleum refining and petrochemical operations, are energy intensive. It is often necessary to conduct these operations at high temperatures using high temperature heat sources including but not limited to steam. After the steam and other hot streams have performed their intended functions, there remains “waste” energy that can be further utilized. Refineries and petrochemical facilities typically utilize only about 70% of the input energy needed to conduct processing of crude oil to products.
In an effort to increase efficiency, it is desirable to recover and utilize unutilized heat. One method described in U.S. Pat. No. 5,823,003 to Rosser et al. attempts to make use of waste heat and apply such heat to an adsorbent material in order to release an adsorbed gas at a higher pressure, which in turn can be used in a power generation or a refrigeration cycle that contains an expansion valve. U.S. Pat. No. 5,823,003 describes the use of a zeolite-water combination for a sorption refrigeration system.
Current methods to obtain refrigeration and work from sorbent materials in chemical process applications have their limitations. The temperature swings (ΔT) afforded using lower grade heat sources, such as waste heat, are less than that which would be provided using primary heat sources. These methods also have longer cycle times. Such limitations often render the recovery of useful from waste heat economically unsustainable.
Accordingly, there remains a need to improve unutilized heat recovery efforts (e.g. waste heat recovery) and render them more cost-effective by providing the opportunity to utilize all grades of unutilized heat, to reduce equipment and space requirements of the process. There also remains a need to provide other uses, besides refrigeration, of the working fluid released from unutilized heat-charged sorbent materials.